This week’s referendum on Scottish independence may seem like an obscure, perhaps even Ruritanian quarrel to many Americans, but it has profound implications not just for the U.K. and Europe but also for the United States.

Most of the debate in the U.K. and elsewhere about Scottish secession has concentrated on whether an independent Scotland could survive or thrive, with a particular focus on whether Scotland would be immediately allowed to join the EU and if it would become a member of NATO despite the official anti-nuclear stance of the Scottish National Party. Very little attention has focused on the likely impact of secession—culturally, psychologically, and economically on the rump United Kingdom.

Great Britain—or whatever the country may be named after the loss of the North of that island—would the only Western European country to lose significant territory since the Second World War. (Various Eastern European countries have split since then, but all of them were relatively recent concoctions, put together in the aftermath of World War I and the destruction of the Austro-Hungarian empire.)

If the British union is dissolved after 300 years, you can expect the impact to be considerably greater than that felt in Russia when the USSR collapsed after a mere 82 years. And we are only beginning to appreciate the extent to which the Soviet collapse affected the morale of the Russian population, prompting a tidal wave of social ills ranging from alcoholism and suicide to catastrophically low birth rates to the rise of virulent ethnic nationalism.

With regard to the latter, it’s worth bearing in mind that “British nationalism” has generally tended to be relatively inclusive and non-racial. However, “English nationalism”, if awakened by Scotland’s secession, is likely to mirror its Scottish and Welsh equivalents and be explicitly racial, with significant potential for ethnic, social and political strife.

Until the last couple of weeks the U.K.’s political class has been remarkably complacent about the referendum, partly because polls had showed a victory for the “No” vote and few had thought much about the possible consequences of secession.

It didn’t help that the commentary in the U.K. press has not been informed by a historical awareness of what happened in other countries when secession was threatened or territory was lost. The Brits seem unaware or to have forgotten that democratic countries like the United States and India have fought bloody wars to prevent secession, or that the loss of Alsace to Germany poisoned French society and politics for more than a generation.

Nor, for that matter, have they noticed that foreign countries, including Britain’s friends and allies, are baffled by the very idea that the U.K. would willingly allow itself to be dismembered.

But, arguably, the most important factor in the inappropriate calmness and inertia of the establishment has been its inability or unwillingness to talk about Britishness. The U.K.’s political class is so uncomfortable with overt expressions of patriotism, and so infected by the multiculturalist critique of British history as simply a narrative of racist, sexist, imperialist violence and exploitation, that it can neither promote nor fight for the union.

Even if a post-referendum secession process were to go as smoothly as that of Czechoslovakia (1918-1992), you can be sure Scotland’s separation from the rest of the U.K. would radically transform and weaken America’s most important military and political ally, perhaps to the point that it might give up its nuclear weapons, its key role in organizations like NATO, and its traditional advocacy of free trade. Such a diminished, demoralized U.K. would not be able, and perhaps not be willing to provide the essential diplomatic or military back-up that Washingon has long taken for granted.

As it is, deep cuts to Britain’s armed forces by the Cameron coalition have eroded the U.K.’s capacity and will to partner with the United States. That decline might become irreversible and permanent if the country is split in two. As for Scotland itself, given the past record of the Scottish National Party, it is likely to join the anti-American chorus at the U.N. and in other international organizations.

Moreover, a U.K. that has let Scotland go (together with its only nuclear submarine base at Faslane) and which could be confronted by more secessionist movements, might soon lose its place as a permanent member of the U.N. Security Council. No likely replacement—be it India, Brazil, or even Germany or Japan—can be counted on to be remotely as supportive of America’s strategic interests.

A “Yes” vote for secession would also set in motion a whole series of political crises across the continent and further afield. Not only is the referendum being closely watched by various nationalist, often left-leaning, secessionist movements around Europe, especially in Spain, Italy and France, but there are representatives of those movements in Scotland helping the nationalists.

If the latter should win, then Catalonia, Corsica, the Basque Country and the Veneto—all of which have well-established separatist parties—will only be the first regions to draw inspiration from the outcome. In Belgium—a relatively recently invented country (est. 1830) that has never succeeded in reconciling its French-speaking (Walloon) and Flemish (Dutch-speaking) populations—Dutch-speaking Flanders is almost certain to seize the moment and set in motion its separation.

Some of these countries are already confronting crises of national identity provoked by the pooling of sovereignty in the European Union, by the euro’s problems, and by mass immigration, in particular from the Muslim world. If more than one of these states is plunged into political, economic or social chaos by invigorated secessionist movements, Europe will become even more of a busted flush than it is already. It’s willingness to resist threats and bribes from Russia will decrease, and its ability to support military campaigns like that in Afghanistan will be even more diminished.

Canada too might experience a resurgence of Quebecois nationalism and simultaneous separatism in its Western states, despite having only just regained its leading position among the liberal democracies.

Finally, Scottish independence could present an immediate security threat to the West and the NATO alliance. The Scottish National Party, though it now talks vaguely about Scotland becoming another Norway (a NATO member which takes seriously its vulnerability to Russian adventurism), has long favored neutrality and unilateral nuclear disarmament. Its instincts, as shown by its reaction to U.S. foreign policy over the last decades are not at all pro-American (the SNP even opposed the NATO interventions to prevent ethnic cleansing in former Yugoslavia).

Worse still, it is believed by Baltic intelligence services that Russia has discreetly lent a hand to Scottish nationalism (Scottish politics are notoriously corrupt by British standards) in the hope of causing as much trouble as possible to the Western alliance.

It is not at all far-fetched to imagine Vladimir Putin offering financial aid to a post-independence Scotland that will inevitably face severe economic challenges.

The price for that aid might include, among other things, basing rights for Russian military and naval forces. Certainly there would be little or nothing that the United Kingdom could do if an independent Scotland decided to rent its deep water submarine port at Faslane to Russia’s Northern fleet or if it let Russian maritime air patrols fly out of former RAF air bases.

That would essentially mean a shifting of NATO’s frontier hundreds of miles to the West and a revolutionary change in the balance of power in Europe.

As was clear from the discussions at the recent NATO summit in Wales, the U.S.-led alliance is already struggling to confront instability and danger in far off Afghanistan, in the chaos of Iraq and Syria, and in nearby Ukraine. Its members will therefore be watching the September 18 vote closely, and hoping for a result that doesn’t gratuitously bring uncertainty and peril to a corner of the world that has, among other virtues, long been a byword for stability, unity and calm.